Wax capsule valves

ABSTRACT

A thermostatic valve in a pneumatic control for a clutch in a cooling fan drive has a sliding spool and two inner valve plungers to connect an actuating ram in the fan hub either to pressure or relief, the clutch being normally engaged by spring pressure. If the supply pressure falls the valve automatically shuts off the pressure to the fan and the fan clutch engages positively by the spring action.

United States Patent [1 1 Elmer WAX CAPSULE VALVES Inventor: ArthurErnest Henry Elmer,

Painswick, England Dynair Limited, Nailsworth, Gloucestershire, GreatBritain [22] Filed: May 21, 1971 [21] Appl. No.: 145,846

Assignee:

[52] US. Cl 236/100, 137/625.69, 192/85 A [51] Int. Cl. .Q G05d 23/275[58] Field of Search l23/4l.12; 192/82 T,

References Cited UNITED STATES PATENTS 8/1957 Herbenar 123/41.12

[ 11 3,738,571 June 12, 1973 Primary ExaminerWil1iam E. WaynerAtt0rney-Young & Thompson [57] ABSTRACT A thermostatic valve in apneumatic control for a clutch in a cooling fan drive has a slidingspool and two inner valve plungers to connect an actuating ram in thefan hub either to pressure or relief, the clutch being normally engagedby spring pressure. If the supply pressure falls the valve automaticallyshuts off the pressure to the fan and the fan clutch engages positivelyby the spring action.

3 Claims, 3 Drawing Figures Patented June 12, 1973 3,738,571

2 manw shmfi 2 WAX CAPSULE VALVES This invention relates to controlvalves, and particularly though not exclusively to thermally actuatedvalves for controlling the supply of a pressure fluid such as compressedair to an actuator such as a pneumatic ram.

The invention is applicable especially to a control valve in a pneumaticcontrol system for a pneumatically operated clutch in the drive to acooling fan of an internal combustion engine. It is known to provide athermally controlled clutch in the drive to a cooling fan, to disengagethe drive when the temperature of the engine falls below a selectedvalue. This is beneficial to the operating efficiency of the engine andmaintains the working temperature at a selected value or within a selected range. The valve of the present invention in its preferred formis designed for use in such a thermally controlled cooling fan drive.

Broadly stated the invention consists in a thermally actuated pneumaticcontrol valve comprising a valve casing having an inlet port and aspaced outlet port, a hollow valve spool slidable in said casing andhaving external sealing means engaging said casing between said inletand outlet ports, and an internal flow passage communicatingrespectively at opposite sides of said sealing means with said inlet andoutlet ports, a movable valve element slidable within said valve spoolto selectively open and close said flow passage, a thermal expansionelement connected to said casing to be exposed externally to temperaturechanges, and having a .movable actuator member projecting into saidvalve casing, spring means acting between said movable valve element andsaid valve spool in a direction to close said flow passage, and pistonmeans connected to said valve element and exposed to air pressureentering said casing via said inlet port and arranged to act on saidvalve element in a direction opposing said spring means.

The valve preferably includes lost-motion means acting between saidmovable valve element and said valve spool, arranged to permit limitedrelative movement to open and close said flow passage during a firstportion of the full range of travel of said movable actuator member, andto cause conjoint movement of said valve spool bodily with said valveelement during another portion of the range of travel of said actuatormember.

According to another preferred feature of the invention the valve casinghas a vent port spaced from said inlet and outlet ports, and said valvespool has a further seal engaging said casing between said outlet portand said vent port, and said movable valve element includes meanscontrolling a further flow passage within said valve spool andcommunicating respectively with said outlet and vent ports on oppositesides of said further seal, whereby said outlet port is selectivelyconnected alternatively to said inlet port or said vent port.

From another aspect the invention consists in a thermally actuatedclutch-controlled cooling fan assembly, including a fan hub carrying aplurality of fan blades,

a clutch associated with said hub for selectively engagmal expansionelement, a movable valve element engaged by said expansion element toselectively open and close a flow passage between an air inlet connectedto said source, and an outlet connected to said actuator, and safetymeans for closing said flow passage in response to a fall in airpressure at said inlet.

In a preferred arrangement said safety means is arranged to close saidflow passage at an air pressure value greater than the pressure value atwhich said spring means becomes operative to cause partial engagement ofsaid clutch. For example said safety means may include a movable pistonelement associated with a movable valve element, and acted upon in onedirection by air at said air inlet pressure, and in the other directionby a balancing spring.

Thus is an object of the invention to provide an improved temperatureoperated control valve which will accommodate the excess movements of atemperature actuator such as a wax capsule outside the normaltemperature range of the capsule. A further object of the invention isto provide a temperature operated valve which will automatically shiftto its closed position if the pressure of the fluid supply falls below apredetermined value. Yet another object of the invention is to provide acooling fan assembly incorporating a pneumatic ram for a clutch in thedrive to the fan, the ram being arranged to disengage the: clutchagainst the force of a spring which acts to engage the clutch, so as toproduce a fail-safe effect, and the valve acts to positively shut-offthe supply of compressed air to the ram if the air pressure falls belowa predetermined value, so preventing partial engagement of the clutch.

The invention may be performed in various ways and one specificembodiment will now be described by way of example with reference to theaccompanying drawings, in which:

FIG. 1 is a sectional side elevation through a thermostatic controlvalve according to the invention,

FIG. 2 is a diagrammatic illustration of a vehicle motor, with a coolingfan, and an automatic clutch control system incorporating the valve ofFIG. 1, and

FIG. 3 is a diagrammatic sectional elevation through the hub of thecooling fan of FIG. 2 illustrating the friction clutch and pneumaticoperating ram.

Refermg first to the complete system illustrated in FIG. 2 the internalcombuston engine 15 is a water cooled petrol or diesel motor arranged todrive the road wheels of the vehicle (not shown), and the motor is alsoarranged to drive a cooling fan having a fan hub 12 and a series of fanblades 13. The cooling circuit of the motor includes a radiator 14through which air is drawn by the fan blades, a water hose 17 throughwhich heated water from the engine cooling jacket passes into the upperpart of the radiator, and a return hose 16 through which water cooled inthe radiator returns to the engine cooling jacket. A water circulatingpump (not shown) is normally included in the water circuit.

The fan hub 12 includes a friction clutch and a pneumatic operating ram,the supply of air to actuate the ram being controlled by thethermostatic valve 10 through which compressed air is delivered from acompressor or other source of compressed air 11 on the vehicle.

The fan hub as illustrated diagrammatically in FIG. 3 comprises a mainrotary outer casing 20, to which the fan blades 13 are attached, thecasing having a part 21 of enlarged diameter at its rear end, in whichis located an annular friction ring or lining 22. This constitutes thedriven element of the friction clutch. The driving element of the clutchis formed by a part-conical flange 23 on a disc 24 which can be attachedby bolts 25 to a flange on the front end of a shaft 26 (see FIG. 2)driven by the engine 15. The clutch is engaged when the casing 20 movesforward relative to the disc 24, Le. to the left in FIG. 3, and isdisengaged when the casing moves in the opposite direction.

The casing 20 is supported via a pair of needle roller bearing races 27on a hollow spigot 28 attached to the driving disc 24. These needleroller bearing races permit relative longitudinal movement of the casing20 in addition to relative rotary movement. Mounted within the hollowspigot 28 is a stem 30, fixed axially with respect to the spigot by aball thrust bearing 31. A radial flange 32, fixed with respect to thecasing 20, projects inwards from the casing towards the stem 30 and hasan inturned flange or lip 33 at its inner edge, which forms a fluidtight seal with the stem 30 via an O-ring seal 34. A helical compressionspring 35 is located between this radial flange or wall 32 and ashoulder or abutment 36 on the stem, which also forms a locatingshoulder for the thrust bearing 31. The spring 35 thus acts to separatethe flange 32 from the should 36 and thus tends to urge the casing 20and the clutch driven member 22 to the left, i.e. in a direction tocause the clutch to engage.

The left hand or front end of the stem 30 is formed with a radial flange40 having an O-ring seal 41 at its outer edge to engage the innersurface of the casing 20 on the forward side of the fixed flange 32. Theannular space 42 between this flange 40 and the flange 32 constitutes apneumatic ram chamber. Compressed air is admitted to and relieved fromthis chamber via a-flexible tube 44 connected to a non-rotary couplingelement 45 which fits in a recess or socket in the front end of the stem30 and is supported by a bearing 46. A rotary air seal (not shown) isalso provided between this coupling 45 and the adjacent parts of thestem 30. As illustrated in FIG. 3 compressed air passing through thetube 44 enters the recess in the stem 30 and passes through a series ofradial drillings 47 into the annular ram chamber 42. When compressed airis admitted to the ram chamber the air pressure acts in oppositedirections on the two flanges 40 and 32 and since the flange 40 isintegral with the stem 30 and is connected via the thrust bearing 31 thedriving disc 24, this flange 40 cannot shift in an axial direction andaccordingly the air pressure causes the flange 32 together with thecasing 20 to shift to the right, so disengaging the cluth. Thus it willbe noted in particular that the clutch is disengaged when air pressureis admitted and is engaged when the air pressure. is cut off orrelieved. This tends to provide a fail safe feature in that if the airpressure should for any reason fail the clutch will automatically engageby reason of the spring 35. It will also be noted however that if theair pressure should merely drop somewhat below the normal operatingvalue the casing 20 could move progressively to the left under theaction of the spring 35 until the clutch partially engages but withoutfull engagement. This would result in clutch slip, ineffectivetransmission of drive to the fan blades 13 and consequent wear of theclutch surfaces. The effect however is effectively reduced or eliminatedby the design of the thermostatic valve as illustrated in detail in FIG.1.

The valve illustrated in FIG. 1 comprises a main hollow generallycylindrical valve chamber or casing 50 having a compressed air inlet 51,a service outlet 52 and a vent port 53, spaced apart longitudinallyalong one side of the casing. One end 54 of the casing is closed and theother end is designed to receive and locate a thermostatic actuator inthe form of a wax capsule 55 filled with a substance such as wax whichis selected for its properties of having a relatively high thermalexpansion rate at a particular selected temperature or temperaturerange. Such wax capsules are well known and need no further description.The capsule is located in the end of the valve casing by a ring 56 whichis anchored by peening-over the end of the casing 57. The capsule issealed to the wall of the casing by an O- ring 58. The actuating memberof the capsule is in the form of a pin or plunger 59 which projects intothe interior of the valve casing and the external surface of the capsuleis in this embodiment exposed to the water flowing through the returnhose 16. The water temperature in this return hose 16 provides the bestindication of the cooling requirements of the engine and automaticallytakes into account such factors as variations in the temperature of theatmosphere or in the speed of movement of the vehicle.

The valve includes three main moving valve elements. The first elementis in the form of a hollow spool or sleeve 60 designed to slidelongitudinally within the casing and having an appreciable clearancearound its external surface. The sleeve is formed with external groovesreceiving O-rings 61,62 which engage and form seals with the innersurface of the valve chamber, these O-ring seals being normallypositioned respectvely between the inlet and outlet ports 51,52 andbetween the outlet port 52 and the vent port 53. When air pressure isadmitted via the inlet 51 the hollow sleeve 60 is urged to the right asillustrated in FIG. 1 and abuts against a ring 63 clamped in position bythe capsule 55. The hollow sleeve 60 has an opening 64 at its left end,through which compressed air can flow from the inlet port 51, a seriesof radial passages 65 positioned between the sealing rings 61,62 and oneor more further passages 66 adjacent its right hand end through whichair can flow to the vent port 53.

The second movable valve element of the valve is in the form of a stemor plunger positioned within the hollow sleeve 60 and having anappreciable clearance therefrom to allow air to flow lengthwise along aninternal flow passage 69 between the two parts 60 and 70. This plunger70 has a pair of annular grooves receiving O-rings 71,72 which engageagainst the internal surface of the hollow sleeve 60. This internalsurface of the hollow sleeve 60 also has two annular grooves ordepressions 73,74, which are of somewhat greater axial length than therespective sealing rings 71,72 and so arranged that when the sealingring 71 is aligned with the groove 73 the seal is ineffective so thatair can flow lengthwise past this seal 71. Similarly when the seal 72 isaligned with the groove 74 compressed air can pass lengthwise around theplunger70 to the right hand end of the valve.

The third valve element is in the form of another plunger which isseparate from and movable independently of the plunger 70, and is alsolocated within and spaced by a clearance from the hollow sleeve 60. Theright hand end of this second plunger 80 has a recess to receive and beengaged by the actuating pin 59 of the wax capsule, and a small annularflange 81 which normally abuts against an inturned shoulder 82 on theleft hand end of the sleeve 60. A light helical compression spring 83 islocated around the plunger 80, one end of the spring abutting againstthis flange 81 and the other end abutting against the right hand end ofthe plunger 70.

The operation of this thermal control valve is as follows. When thetemperature of the water in the return hose 16 is below the selectedoperating value the actuating pin 59 of the wax capsule is withdrawn tothe right as illustrated in FIG 1. Compressed air which is permanentlyavailable at the air inlet 51 while the engine is running, acts in theright hand direction on the hollow sleeve 60 and also on the movablevalve element 70 urging both these components to the right as shown inFIG. 1. In this position the sealing ring 71 is aligned partly with theinternal groove 73 and air can thus flow through the clearance aroundthe plunger 70 from left to right, through the radial passage 65 to theoutlet 52. From this service port 52 the compressed air passes via theflexible tube 44 to the fan hub where it acts in the manner describedabove to cause the clutch to be disengaged. This avoids wastage of powerin driving the cooling fan unnecessarily and also avoids over-cooling sothat the engine temperature can more rapidly rise to its optimum value.

As the temperature of the cooling water in the return hose 16 rises theactuating pin 59 of the capsule projects into the valve chamber, engagesthe second valve plunger 80 and moves this plunger together with theplunger 70 to the left. After a short travel of the plunger 70 thesealing ring 71 passes beyond the groove I 73 and forms sealingengagement with the internal surface of the hollow sleeve 60 beyond thisgroove, thus blocking off the flow of air between the air inlet port 51and the service port 52. Simultaneously (or prefera bly shortlyafterwards when the plunger 70 has moved a further short distance to theleft) the second sealing ring 72 becomes aligned with the groove 74, andthis interrupts the seal between the service port 52 and the vent port53 so that air from the service port and the pneumatic ram chamber 42can exhaust via the vent port 53.

If the water temperature continues to rise and the capsule actuating pin59 extends further to the left, the left hand end of the plunger 70engages a spring clip 85 positioned in the left hand end of the hollowsleeve 60 and further movement of the actuating pin 59 causes the sleeve60 to move bodily to the left together with the two plungers 70 and 80.This avoids imposing any restraint on the actuating element of the waxcapsule and also avoids the need for excessve longitudinal intervalsbetween the seals 71 and 72 and between the annular grooves 73,74. Ifthe temperature of the cooling water in the hose 16 should fall theactuating pin 59 will return or withdraw into the capsule and thesequence of operations is reversed; firstly the service port 52 isdisconnected from the vent port 53, and subsequently reconnected withthe air inlet 51, thus again admitting compressed air to the ram of theclutch so that the clutch is disengaged.

As explained above the valve also includes means for avoiding partialengagement of the clutch if the inlet air pressure should fall below apredetermined value. This is achieved by the light compression spring 83which tends to separate the two plungers 70 and 80. Normally anypressure at the air inlet 51 acts on the left hand end of the plungerand causes this plunger to abut against the end of the plunger 80, whosemovements are controlled by the capsule actuating pin 59. The airpressure is normally more than sufficient to overcome the force of thespring 83. If the air pressure should fall for any reason then at apredetermined pressure the spring 83 will over come the effect of thepressure acting on the left hand end of the plunger 70 and will causethis plunger to move relatively to the left until it auts against thespring clip 85 sothat the seal 71 forms sealing engagement with innersurface of the sleeve 60 and so blocks communication between the airinlet 51 and the service port 52. This shut-off is positive and in thepresent example occurs when the inlet air pressure falls below 65 p.s.i.This value is selected to be above the value (in this example about 55p.s.i.) at which the clutch would itself tend to engage as a result of afall in pressure in the actuating ram chamber 42. In other words thevalve will automatically shut off the compressed alr supply to the fanclutch before the air pressure has fallen to a point at which the clutchitself would automatically tend to disengage. Thus the action of theclutch in the event of a failure or partial failure of the air supplywill be positive so that the clutch will engage fully, so providing afull drive to the fan blades and avoiding wear of the clutch surfaces.

I claim:

1. A thermally actuated pneumatic control valve, comprising a valvecasing having an inlet port and a spaced outlet port, a hollow valvespool slidable in said casing and having external sealing means engagingsaid casing between said inlet and outlet ports, and an internal flowpassage communicating respectively at opposite sides of said sealingmeans with said inlet and outlet ports, a movable valve element slidablewithin said valve spool to selectively open and close said flow passage,a thermal expansion element connected to said casing to be exposedexternally to temperature changes, and having a movable actuator memberprojecting into said valve casing and acting on at least said movablevalve element in a direction to close said flow passage upon thermalexpansion, and spring means acting between said movable valve elementand said valve spool in a direction to close said flow passage, saidmovable valve element being exposed to air pressure entering said casingvia said inlet port and acting on said valve element in a directionopposing said spring means.

2. A control valve according to claim 1, including lost motion meansacting between said movable valve element and said valve spool, arrangedto permit limited relative movement to open and close said flow passageduring a first portion of the full range of travel of said movableactuator member, and to cause conjoint movement of said valve spoolbodily with said valve element during another portion of the range oftravel of said actuator member.

3. A control valve according to claim 1, in which said valve casing hasa vent port spaced from said inlet and outlet ports, and said valvespool has a further seal engaging said casing between said outlet portand said vent port, and said movable valve element includes meanscontrolling a further flow passage within said valve spool andcommunicating respectively with said outlet and vent ports on oppositesides of said further seal, whereby said outlet port is selectivelyconnected alternatively to said inlet port or said vent port.

1. A thermally actuatEd pneumatic control valve, comprising a valvecasing having an inlet port and a spaced outlet port, a hollow valvespool slidable in said casing and having external sealing means engagingsaid casing between said inlet and outlet ports, and an internal flowpassage communicating respectively at opposite sides of said sealingmeans with said inlet and outlet ports, a movable valve element slidablewithin said valve spool to selectively open and close said flow passage,a thermal expansion element connected to said casing to be exposedexternally to temperature changes, and having a movable actuator memberprojecting into said valve casing and acting on at least said movablevalve element in a direction to close said flow passage upon thermalexpansion, and spring means acting between said movable valve elementand said valve spool in a direction to close said flow passage, saidmovable valve element being exposed to air pressure entering said casingvia said inlet port and acting on said valve element in a directionopposing said spring means.
 2. A control valve according to claim 1,including lost motion means acting between said movable valve elementand said valve spool, arranged to permit limited relative movement toopen and close said flow passage during a first portion of the fullrange of travel of said movable actuator member, and to cause conjointmovement of said valve spool bodily with said valve element duringanother portion of the range of travel of said actuator member.
 3. Acontrol valve according to claim 1, in which said valve casing has avent port spaced from said inlet and outlet ports, and said valve spoolhas a further seal engaging said casing between said outlet port andsaid vent port, and said movable valve element includes meanscontrolling a further flow passage within said valve spool andcommunicating respectively with said outlet and vent ports on oppositesides of said further seal, whereby said outlet port is selectivelyconnected alternatively to said inlet port or said vent port.